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Factors Affecting India's Climate




  • The Tropic of Cancer passes through the middle of India affecting its climate considerably.
  • The Tropic of Cancer extents from the Rann of Kuchchh in the west to Mizoram in the east.
  • The southern half of the country lies south of the Tropic of Cancer, and belongs to the tropical area.
  • The northern half of the country which lies to the north of the Tropic of Cancer belongs to the sub- tropical area.
  • Therefore, India has characteristics of both tropical as well as subtropical climates.

Tropical Climate
In India the Tropical climate may be divided into tropical wet and dry climate.

  • A tropical wet climate covers regions experiencing persistent warm or high temperatures, which normally do not fall below 18 °C.
  • A tropical dry climate covers regions where the rate of moisture loss through evaporation exceeds that from precipitation.
  • Sub-tropical Climate

  • Sub-tropical climate covers most of Northeast India and much of North India are subject to a humid sub-tropical climate. Though they experience hot summers, temperatures during the coldest months may fall as low as 0 °C .




  • India is bounded by mountains in the north. The average height of these mountains are about 6,000 metres.
  • India has a vast coast line where the maximum elevation is about 30 metres.
  • The Himalayas prevent the cold winds from Central Asia from entering the subcontinent.
  • The altitude of these mountains make the Indian subcontinent experiences comparatively milder winters than Central Asia.

    Pressure and Winds

    Atmospheric conditions such as Pressure and Winds govern the climatic conditions in India.

    Atmospheric conditions can be classified as :-
    • Pressure and surface wind.
    • Upper air circulation.
    • Western cyclonic disturbances and tropical cyclones.

    North Easterly Winds

  • India lies in the region of the north easterly winds.
  • These winds start from the subtropical high-pressure belt of the northern hemisphere.
  • They blow southwards and get deflected to the right due to the Coriolis force.
  • The Coriolis force is the result of the Earth’s rotation. If a low-pressure area forms in the atmosphere, air will tend to flow towards it, but the air will be deflected perpendicular to its velocity by the Coriolis force. A system of equilibrium is established creating a circular movement, or a cyclonic flow.


    The north easterly winds then move towards the equatorial low-pressure area.
    • These winds bring little or no rain as they originate and blow over land.

    South Westerly Winds

    • The South Westerly Winds originate from the southern Indian Ocean.
    • They move in a south-easterly direction and cross the Equator.
    • After they cross the Equator they turn right towards the low-pressure areas over India.
    • This low-pressure area develops over interior Asia as well as over north western India during summer.
    • As the South Westerly Winds blow over the warm oceans, gather moisture and bring widespread rainfall over the India.

    Now let us look at the High and low pressure areas that determine the flow of wind.

    Wind flows from a high pressure area towards a low pressure area.

    • During the winter season, high pressure area develops north of the Himalayas and the wind flows towards the low-pressure area formed over the oceans in the south.
    • During summer high pressure area develops over the southern Indian Ocean and the wind flows towards the low-pressure area formed over the Indian subcontinent.

    So, there is a complete reversal to the direction in which the wind during winter and during summer.
    We have seen that air moves from a high pressure area towards a low pressure area. An important component of this flow is the jet stream.


    The Jet Stream

    Jet streams are fast flowing, narrow air currents found in the atmosphere at around 11 kilometers above the surface of the Earth. They form at the boundaries of adjacent air masses which have significant differences in temperature, such as of the polar region and the warmer air to the south. The jet stream is mainly found between the troposphere and the stratosphere. The major jet streams are westerly winds which flow from the west to east. The path of the jet has a typically meandering shape.

    Subtropical Jet Streams


    These jet streams are known as subtropical westerly jet streams. These jet streams blow south of the Himalayas, all through the year except in summer.

    The western cyclonic disturbances experienced in the north and north-western parts of the country are brought in by this westerly flow.

    In summer, the subtropical westerly jet stream moves north of the Himalayas with the movement of the sun.

    An easterly jet stream, called the tropical easterly jet stream blows over peninsular India, approximately over 14°N during the summer months.

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